1. Field of the Invention
The present invention relates generally to tape cassettes, and is particularly directed to improvements in Phillips-type compact cassettes, such as are used in tape recorders and dictating machines.
2. Description of the Prior Art
Frequently, in compact cassettes, in order to increase the strength and useful life of the cassette casing, the usual upper and lower halves of the cassette casing are formed, for the most part, of a desirably strong non-transparent synthetic resin, such as, ABS resin, or a non-transparent metal, such as, aluminum, and window openings of relatively small size and which are closed by similarly small window members of transparent or semitransparent synthetic resin are provided only at the central portions of the upper and lower casing halves, respectively. Although such compact cassettes are sufficiently strong, the user cannot view the interior of most of the cassette casing, and thus cannot examine the condition of all of the tape wound on the reel hubs, and also cannot determine whether the tape extending between the hubs is properly engaged with the guides therefor. In order to overcome the foregoing disadvantage, a tape cassette has been made available in which the sizes of the window openings and the respective transparent window members included in the upper and lower casing halves have been substantially enlarged to permit the user to more fully view the interior of the casing.
However, as the size of the window member increases, the lengths of the welds by which the sides of the window member are secured, as by ultrasonic welding or the like, to the opaque frame or remaining portion of the respective casing half are increased accordingly. Weld defects tend to occur with increasing frequency upon such increases in the weld lengths. When such weld defects occur, the window members may be accidentally removed from the respective window openings as a result of impacts, vibrations or pressures applied to the cassette casing. In order to prevent such inadvertent removal of the enlarged window members from the respective window openings of the cassette casing, it has been proposed to employ a suitable adhesive, rather than ultrasonic welding, for securing each window member to the respective frame, or to provide dowels extending from the peripheral portion of the window member to be passed through holes in the respective frame and then upset or headed by pressure for preventing removal of the window member from the frame. However, such use of adhesive or upsetting of dowels for reliably securing the window members to the respective frames are time consuming, and thus reduce productivity and substantially increase the cost of manufacture of the cassette casings.
Furthermore, when the window members of the cassette casing are enlarged, as aforesaid, it becomes difficult to mount other components of the tape cassette, such as, tape guide rollers and friction bosses, at proper positions within the cassette casing. Although various procedures have been proposed, they usually involve cumbersome assembling steps and also the use of casing halves which are asymmetrical relative to each other, thereby decreasing the commercial attractiveness of the cassette casing.